The present invention relates to an improved pesticide spraying apparatus for use in the application of agricultural pesticides. This improved apparatus utilizes a rotary atomizer, such as the atomizer described in U.S. Pat. No. 4,225,084, as a pesticide droplet discharge unit.
The most common method of applying agricultural pesticides necessitates the use of large volumes of water as a carrier for the chemical. However, many problems have been encountered which have caused the agricultural industry to look for alternative methods of application. One of the major problems in the use of water as a carrier is that 20-30 gallons of water per application acre is required to achieve acceptable coverage. The need for such large volumes creates hardships due to the containment and transfer operations needed to replenish the sprayer holding tanks with the appropriate chemical mix. In some instances, the operator must discontinue spraying operations every few acres to replenish his tanks. Further, most commonly used pesticides available on today's market are not water soluble, but rather are oil-based. These oil-based pesticides require additives which allow the pesticide to properly mix with the water. Without the additives, the water and oil pesticide mixture sometimes forms an inversion during agitation; an undesirable condition. Problems have also been encountered in environments that are hot, dry and windy as the water carrier may evaporate entirely within seconds after application, thereby not allowing the pesticide chemical to be effectively absorbed.
The rotary atomizer technology, such as that disclosed in U.S. Pat. No. 4,225,084, has made available a pesticide applicator which is capable of more closely regulating the volume of chemical used and thereby regulating the chemical cost to the farmers. The rotary atomizer unit provides for an ultra low volume, controlled droplet discharge which greatly enhances reduced chemical application rates and provides for improved pest control. Such atomizers have been found to be acceptable applicators for a non-water approach to pesticide application. The use of the rotary atomizer promotes uniform droplet size and improves droplet density to increase the effectiveness of the chemical pesticide treatment as compared to other conventional application methods. Further, the low volume design of the atomizer cup produces acceptable results from both direct rate application and oil-based rate application, as an alternative to water based application.
As long as a sufficient number of droplets of acceptable size can be generated by the rotary atomizer, there is no need for a carrier. If a larger volume of droplets is necessary, a compatible oil carrier can be used. The use of vegetable oil as a replacement for water as a carrier has solved several problems. Vegetable oil eliminates alkaline hydrolysis wherein the salts in the water neutralize the acid in the pesticide. Vegetable oil improves the efficacy of the pesticide chemical since it is biologically active and can be absorbed or digested by the plant or insect being treated. Vegetable oil greatly reduces the rates of chemical volatility and the photodecomposition of some pesticide chemicals. Also, vegetable oil resists washoff and spreads out to provide a more even application.
Certain current models of the rotary atomizer type applicator use small DC motors to drive the atomizers. Early versions of the DC motor drive systems encountered problems in reliability because pesticide chemicals being applied were highly corrosive to the atomizer unit and its drive systems. As the drive system corrodes, power to the motors was frequently interrupted causing an inordinate amount of service and down time. Further, the commonly used DC electric motors are operable only at a limited range of speeds; for example four distinctly different speeds. The limited speed settings can cause incorrect application rates. For instance, if the atomizer is set at too high a speed for wind conditions at the time of application, the droplets will be quite fine and will drift from the target area. However, if the speed of the atomizer is reduced to eliminate the drift of the pesticide, the large droplet size which can result from the limitations on speed variations will result in wasted chemicals and will not provide adequate coverage.
In an attempt to correct these shortcomings, some rotary atomizers have been designed which use individual hydraulic drive motors. The use of hydraulic motors has provided for a greater variation in speed settings as the hydraulic motors are controlled by manually adjusting their hydraulic flow. This approach has encountered significant problems in that the hydraulic motors consume large volumes of high pressure oil; more oil than most small and medium size prime movers can provide without the addition of an auxiliary hydraulic system. Further, since the motors are directly coupled to the atomizer cup, they must rotate at (whatever cup) speed is needed by the cup to adequately disperse the pesticide chemical. These cup speeds can approach 6,000 revolutions per minute in some applications. Such high speeds can create foaming in the hydraulic oil as well as overheat the oil. The hydraulic oil often reaches temperatures near or above design limits. In order to reduce the overheating problems, auxiliary cooling systems have been required on all but the largest tractors which usually have such systems as standard equipment. These cooling systems prevent the breakdown of the hydraulic oil and, thereby, increase the life of all components which are lubricated by the hydraulic system. Even with large tractors and ideal hydraulic systems, however, the individual hydraulic motors are known to wear at uneven rates after only a few weeks of use. Long before the service life of the motor is over, measurable differences between atomizer speeds will result in uneven application rates.
Other attempts to improve the efficacy of the rotary atomizer include the use of small fans attached to the shaft at the bottom of the atomizer. These fans are intended to help direct the pesticide spray. The fans can be manually adjusted to provide a variable pitch to increase and decrease air delivery speeds. They rotate at the same speed as the rotary atomizer and there are many limitations in their ability to deliver desirable volumes of air. The fans are able to increase or decrease air velocity at a given RPM only by adjusting the pitch of the blades. However, this adjustment must be manually made to each individual blade; a frustrating and time-consuming chore.
Application environments that need varying degrees of large droplets and large volumes of air or small droplets and small volumes of air cannot be adequately treated without many time-consuming manual adjustments being made to the spray system by the operator. The operator has to leave the tractor platform and adjust each unit whenever change is required. Thus, when working in small fields where crop conditions often change, the continual readjustment process can easily consume large quentities of an operator's time.
Therefore, it is the purpose of the present invention to provide an improved pesticide spraying apparatus capable of an infinite variety of adjustable speeds at the rotary atomizer and further being capable of an infinite variety of independently adjustable speeds of a fan blower to assist in dispersion of the pesticide chemical.